Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle- or large-sized devices, such as vehicles, use a middle- or large-sized battery module having a plurality of battery cells electrically connected to one another because high power and large capacity are necessary for the middle- or large-sized devices.
Preferably, the middle- or large-sized battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle- or large-sized battery module. Especially, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the weight of the pouch-shaped battery is small, the manufacturing costs of the pouch-shaped battery are low, and it is easy to modify the shape of the pouch-shaped battery.
Meanwhile, a battery module is a structural body including a plurality of battery cells which are combined with each other, with the result that the safety and the operating efficiency of the battery module may be lowered when overvoltage, overcurrent, and overheating occur in some of the battery cells. Consequently, a sensing unit for sensing the overvoltage, overcurrent, and overheating is needed. Specifically, a voltage sensor or a temperature sensor is connected to the battery cells so as to sense and control the operation of the battery cells in real time or at predetermined time intervals.
That is, a wire type connection member is used as a channel for transmitting voltages and temperatures of the battery cells to a battery management system (BMS). The wire type connection member may be implemented by, for example, a bundle of sheathed data cables, at each end of which may be provided a plug or cap type connector.
However, if moisture is formed on the surface of the wire type connection member due to change in temperature of the battery cells during charge and discharge of the battery cells, the moisture on the wire type connection member is introduced to the connection part located at the corresponding end of the wire type connection member along the surface of the wire type connection member due to gravity unless the connectors provided at the ends of the wire type connection member have a waterproof function. As a result, a short circuit may occur at a coupling region between the connection part and the connection counterpart.
Also, the BMS electrically connected to the connection counterpart measures a voltage value of each battery cell. For this reason, accurate sensing is needed, and therefore, it is necessary to provide a wire type connection member of a specific structure that is capable of preventing the occurrence of a short circuit.
Consequently, there is a high necessity for a middle- or large-sized battery module including a wire type connection member of a specific structure that is capable of preventing the occurrence of a short circuit between a coupling region between a connection part and a connection counterpart due to moisture as described above and thus the occurrence of a short circuit in battery cells.